On Fri, 2009-05-08 at 21:58 -0400, Nick Nobody wrote: > On May 8, 2009 08:04:11 pm Andy Walls wrote: > > On Fri, 2009-05-08 at 16:56 -0400, Nick Nobody wrote: > > > Hello, > > > > > > I just got a HVR1600 and am trying to build a channels.conf file with all > > > the channels that I get using my TV (it has a built-in ATSC tuner). > > > > Are you using the cx18, mxl5005s and s5h1409 drivers that came with your > > distribution or the latest v4l-dvb repository drivers? > > > > If not the latest, you should try those first. See the cx18 page on > > ivtvdriver.org for instructions on getting the latest drivers. > > > > http://www.ivtvdriver.org/index.php/Cx18 > > > > > I use the following command to scan for channels (on mythbuntu 9.04): > > > > > > scan /usr/share/dvb/atsc/us-ATSC-center-frequencies-8VSB > > > > > > It manages to find every single channel except for WFFF-TV (aka FOX44). > > > My television shows that it has a strong signal strength and is actually > > > better than some other channels. > > > > According to the FCC, WFFF-TV's digital station is on UHF channel 43. > > How does WFFF's analog station look on UHF channel 44? Any snow, > > ghosting, or interference lines? > > > > If so, that indicates poor reception from that transmitter. If so, also > > please review: > > > > http://www.ivtvdriver.org/index.php/Howto:Improve_signal_quality > > > > > Is there something I can do help the scan program > > > find this channel? > > > > Well, if it helps, the center freq for an ATSC-8VSB channel on UHF > > channel 43 is 647.028615 MHz. > > > > Maybe you could make up a manual entry in channels.conf, azap to it, and > > then use femon or dvbtraffic to see if you can get a lock and see the > > PIDs in use. > > > > Where I'm at, PIDs 0x31 (49) and 0x34 (52) are usually in use for the > > primary video and audio program. > > > > > I noticed that it's one of the few (or only) channel that > > > broadcasts in 720p instead of 1080i, but I doubt that makes much of a > > > difference... > > > > It shouldn't make a difference. > > > > Regards, > > Andy > > > > > Thanks, > > > > > > nick > > > > Hi Andy, > > Thanks for the quick and detailed response. > > It seems that you're right about it being a signal strength issue because as > soon as the sun went down I was able to (unreliably) find the channel with a > scan.
That can happen when the main beam of your antenna (or a sidelobe) is pointed at an an object in the sky with a high noise/brightness temperature (the sun or the galactic disk). When that bright object is seen by your antenna, the noise degrades the signal to noise ratio. You may want to focus on steps to reduce noise: gounding the coax shield to reduce EMI and adding a low-noise preamplifier. > I've gone through all of your recommendations and here's what I've come > up with: > > Using the latest drivers makes it much harder for me to get a lock, I had > better results with version 1.0.4 that comes with the vanilla 2.6.29 kernel > (I'm using the prepackaged 2.6.29 ubuntu kernel: 2.6.29-02062902). That's surprising. AFAIK, there was possibly one change to the s5h1409 driver to make it tune faster, by reseting the digital demodulator's tracking to help it lock on to the new signal faster. You may just have good luck with the old driver by being tuned to a certain station before going to WFFF. > 44 is just snow for me, but I'm assuming that's because their analog > transmitter is off-air. All the wiring is new, in fact there's only one > splice > (union) from the antenna down to the capture card. OK. Please ensure you're using a splitter and not a splice; as a splitter is needed to match impedences properly. Also make sure you've got a grounding block (connected to green wire ground) in the coaxial cable as close as possible to where the coaxial cable attaches to the antenna to ground the shield of the coax. Reducing EMI made a big difference for me. > As mentioned above, I was able to get a lock tonight and was able to watch > the > channel for a good 25min but then it just crapped out. Is there a way to > increase the sensitivity of the card? I don't have data on the MXL5005s tuner nor the data on the discrete components wired up to it. Without that, I have no hope of tweaking the mxl5005s configuration to make the reception better. :( I personally use a low noise (2.9 dB NF), high gain (29 dB) VHF/UHF preamp from Winegard for my home. It's an AP-8275: http://www.winegard.com/offair/preamp.php http://www.winegard.com/kbase/upload/chart29.pdf It works great for me, because I live so far from the city. The 29 dB gain can overdrive tuners (and thus degrade reception), if you live where signals are of decent strength, so a low-noise preamp with less gain is better in most situations. > My television (which has a much longer > length of wire going to it) has a perfect picture day or night; I don't > understand why it works while the HVR1600 doesn't :S Have you tried connecting the HVR-1600 to the wire feeding your television? Regards, Andy > Thanks for your help, > > nick _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
